India Monsoon Record Since The Middle Pleistocene In The Andaman Sea

The India monsoon is a part of the earth's climate system.It is the most powerful tropical monsoon system in the world and plays an important role in the earth's environmental system.The India monsoon,which directly affects the global scale of atmospheric circulation,ocean circulation and the transportation of water vapor,has an important role in driving and responding to the global climate change.Its precipitation changes have an important impact on the agricultural production and social and economic development of the world's one fourth population in South Asia.So,the study of the India monsoon is an international hot topic in the science of ocean and climate change.From November 2014 to January 2015,the International Ocean Discovery Program(IODP)353 "India monsoon" has obtained sediment samples at 6 sites in the Bay of Bengal and the Andaman Sea.It aims to deepen the research on the driving mechanism of India monsoon in the core area of monsoon rainfall in India.In this study,through the analysis of planktonic foraminifera assemblages from the sediments at the Site U1448 in the Andaman Sea,the characteristics of the Paleoenvironment were rebuilt to provide a theoretical basis for explaining the relationship between the precipitation of India monsoon and the hydrological environment changes in the Andaman Sea area since the period of MIS9.It is found that the dissolution of carbonate at Site U1448 is weak,and the assemblage of foraminiferal fossils is relatively well preserved,and the abundance of planktonic and benthic foraminifera abundances is characterized by high abundance the interglacial period and low in glacial.The dominant species of planktonic foraminiferal are Globigerinoides ruber?Globigerinoides bulloides?Globigerinoides glutinata?Neogloboquadrina dutertrei ? Pulleniatina obliquiloculata,which exhibit a typical tropical-subtropical combination.The change of productivity reflected by the deposition flux of planktonic and benthic foraminifers and the high productivity species(G.bulloides and G.glutinata)reflects the trend of the India summer monsoon.During the interglacial period(MIS1,MIS3,MIS5 and MIS7),the summer monsoon enhanced and the surface productivity increased,while in the glacial period the summer monsoon showed a weak trend and the surface productivity decreased.It is presumed that when the summer monsoon enhanced,a strong clockwise circulation was formed in the Bay of Bengal,bringing nutrients along the west side from the south of Bay of Bengal,resulting in a rise in surface biological productivity,but the salinity of the surface water did not decrease significantly.